Semiconductor device having bent portion

ABSTRACT

A display device includes a base film including a first region and a plurality of second regions having the first region therebetween; an inorganic insulating film on the base film, the inorganic insulating film being in contact with the plurality of second regions of the base film; a plurality of first pixels overlapping the first region; and a plurality of second pixels overlapping the plurality of second regions with the inorganic insulating film being between the plurality of second pixels and the plurality of second regions. The inorganic insulating film is divided by the first region and is discontinuous between the plurality of second regions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/812,461, filed on Mar. 9, 2020, which, in turn, is a continuation ofU.S. patent application Ser. No. 15/792,955 (now U.S. Pat. No.10,620,464), filed on Oct. 25, 2017. Further, this application is basedupon and claims the benefit of priority from the prior Japanese PatentApplication No. 2016-220419, filed on Nov. 11, 2016, the entire contentsof which are incorporated herein by reference.

FIELD

One of embodiments of present invention relates to a display device suchas an organic EL display device, a liquid crystal display device or thelike, and a method for producing the same, for example, a flexibledisplay device and a method for producing the same.

BACKGROUND

Representative display devices include a liquid crystal display deviceincluding a liquid crystal element in each of pixels, an organic EL(electroluminescence) display device including a light emitting elementin each of pixels, and the like. These display devices each include aliquid crystal element or an organic light emitting element(hereinafter, referred to as a “light emitting element”) in each of aplurality of pixels provided on a substrate. The liquid crystal elementor the light emitting element includes a layer containing a liquidcrystal material or an organic compound between a pair of electrodes(hereinafter, the layer containing the organic compound will be referredto as an “organic layer” or an “EL layer), and is driven by a voltageapplied between the pair of electrodes or by a current supplied to thepair of electrodes.

The substrate of such a display device may be flexible, so that aflexible display device is provided. For example, Japanese Laid-OpenPatent Publication No. 2011-183916 discloses a display device includinga flexible substrate and a plurality of display regions provided on thesubstrate. The substrate is folded at an optional angle at a positionbetween the display regions, so that a plurality of display devices isprovided on different curved surfaces.

SUMMARY

An embodiment of the present invention is directed to a display device.The display device includes a base film including a first region and aplurality of second regions having the first region therebetween. Thedisplay device further includes an inorganic insulating film on the basefilm, the inorganic insulating film being in contact with the pluralityof second regions of the base film; a plurality of first pixelsoverlapping the first region; and a plurality of second pixelsoverlapping the plurality of second regions with the inorganicinsulating film being between the plurality of second pixels and theplurality of second regions. The inorganic insulating film is divided bythe first region and is discontinuous between the plurality of secondregions.

An embodiment of the present invention is directed to a display device.The display device includes a base film including a first region and asecond region; an underlying film on the base film, the underlying filmbeing in contact with the first region and the second region of the basefilm; and a plurality of first pixels overlapping the first region and aplurality of second pixels overlapping the second region. The pluralityof first pixels and the plurality of second pixels each include asemiconductor film and a gate electrode overlapping each other; and agate insulating film between the semiconductor film and the gateelectrode. The underlying film is thinner on the first region than onthe second region.

An embodiment of the present invention is directed to a display device.The display device includes a base film including a first display regionincluding a plurality of first pixels, a second display region includinga plurality of second pixels, and a first region between the firstdisplay region and the second display region; and an inorganicinsulating film overlapping the base film in the first display regionand the second display region. The first region of the base film isexposed from the inorganic insulating film.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic perspective view of a display device in anembodiment according to the present invention;

FIG. 2 is a schematic exploded perspective view of the display device inan embodiment according to the present invention;

FIG. 3 is a schematic plan view of the display device in an embodimentaccording to the present invention;

FIG. 4 is a schematic cross-sectional view of the display device in anembodiment according to the present invention;

FIG. 5 is a schematic plan view of the display device in an embodimentaccording to the present invention;

FIG. 6A is a schematic cross-sectional view of a pixel of the displaydevice in an embodiment according to the present invention;

FIG. 6B is a schematic cross-sectional view of a pixel of the displaydevice in an embodiment according to the present invention;

FIG. 7 is a schematic perspective of the display device in an embodimentaccording to the present invention;

FIG. 8A is a schematic cross-sectional view of a pixel of a displaydevice in an embodiment according to the present invention;

FIG. 8B is a schematic cross-sectional view of a pixel of the displaydevice in an embodiment according to the present invention;

FIG. 9A is a schematic cross-sectional view showing a step of a methodfor producing a display device in an embodiment according to the presentinvention;

FIG. 9B is a schematic cross-sectional view showing a step of the methodfor producing the display device in an embodiment according to thepresent invention;

FIG. 10A is a schematic cross-sectional view showing a step of themethod for producing the display device in an embodiment according tothe present invention;

FIG. 10B is a schematic cross-sectional view showing a step of themethod for producing the display device in an embodiment according tothe present invention;

FIG. 11A is a schematic cross-sectional view showing a step of themethod for producing the display device in an embodiment according tothe present invention;

FIG. 11B is a schematic cross-sectional view showing a step of themethod for producing the display device in an embodiment according tothe present invention;

FIG. 12A is a schematic cross-sectional view showing a step of themethod for producing the display device in an embodiment according tothe present invention;

FIG. 12B is a schematic cross-sectional view showing a step of themethod for producing the display device in an embodiment according tothe present invention;

FIG. 13A is a schematic cross-sectional view showing a step of themethod for producing the display device in an embodiment according tothe present invention;

FIG. 13B is a schematic cross-sectional view showing a step of themethod for producing the display device in an embodiment according tothe present invention;

FIG. 14 is a schematic cross-sectional view showing a step of the methodfor producing the display device in an embodiment according to thepresent invention;

FIG. 15 is a schematic cross-sectional view showing a step of the methodfor producing the display device in an embodiment according to thepresent invention;

FIG. 16 is a schematic cross-sectional view showing a step of the methodfor producing the display device in an embodiment according to thepresent invention;

FIG. 17 is a schematic cross-sectional view showing a step of the methodfor producing the display device in an embodiment according to thepresent invention;

FIG. 18 is a schematic plan view of a display device in an embodimentaccording to the present invention;

FIG. 19 is a schematic cross-sectional view of the display device in anembodiment according to the present invention;

FIG. 20A is schematic plan view of a display device in an embodimentaccording to the present invention;

FIG. 20B is schematic plan view of a display device in an embodimentaccording to the present invention;

FIG. 21 is schematic plan view of a display device in an embodimentaccording to the present invention;

FIG. 22 is schematic cross-sectional view of the display device in anembodiment according to the present invention;

FIG. 23A is a plan view of wirings in the display device in anembodiment according to the present invention;

FIG. 23B is a plan view of wirings in the display device in anembodiment according to the present invention;

FIG. 23C is a plan view of wirings in the display device in anembodiment according to the present invention;

FIG. 24 is a plan view of wirings in the display device in an embodimentaccording to the present invention;

FIG. 25 is a schematic plan view of a display device in an embodimentaccording to the present invention; and

FIG. 26 is a schematic plan view of a display device in an embodimentaccording to the present invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the drawings and the like. The present invention may becarried out in various forms without departing from the gist thereof,and is not to be construed as being limited to any of the followingembodiments.

In the drawings, components may be shown schematically regarding thewidth, thickness, shape and the like, instead of being shown inaccordance with the actual sizes, for the sake of clearer illustration.The drawings are merely examples and do not limit the interpretations ofthe present invention in any way. In the specification and the drawings,components that have substantially the same functions as those describedbefore with reference to a previous drawing(s) bear the identicalreference signs thereto, and detailed descriptions thereof may beomitted.

In the present invention, in the case where one film is processed into aplurality of films, the plurality of films may have different functionsor roles from each other. However, the plurality of films is derivedfrom one, same film and are formed in the same step, and thus have thesame layer structure and are formed of the same material as each other.Therefore, the plurality of films is defined as being in the same layer.

In the specification and the claims, an expression that a component is“on” another component encompasses a case where such a component is incontact with the another component and also a case where such acomponent is above or below the another component, namely, a case wherestill another component is provided between such a component and theanother component, unless otherwise specified.

The embodiments of the present invention have an object of providing ahighly reliable and flexible display device. The embodiments of thepresent invention have an object of providing a method for producingsuch a display device.

Embodiment 1

In this embodiment, a structure of a display device 100 in an embodimentaccording to the present invention will be described.

1. Overall Structure

FIG. 1 is a schematic perspective view of the display device 100. Asshown in FIG. 1, the display device 100 includes a substrate 102, acounter substrate 104, and a plurality of pixels 106 located in a rowdirection and a column direction between the substrate 102 and thecounter substrate 104. A region where the plurality of pixels 106 arelocated is a display region 108.

The plurality of pixels 106 each include a display element such as aliquid crystal element, a light emitting element or the like. Thedisplay device 100 further includes scanning line driving circuits 110and a data line driving circuit 112 provided on the substrate 102.Various signals usable to drive the pixels 106 are input from anexternal circuit (not shown) to the scanning line driving circuits 110and the data line driving circuit 112 via a connector such as a flexibleprinted circuit (FPC) or the like connected to terminals 114 provided onthe substrate 102. Based on these signals, the display element in eachpixel 106 is controlled, so that an image is reproduced in the displayregion 108.

The scanning line driving circuits 110 or the data line driving circuit112 does not need to be provided directly on the substrate 102.Alternatively, neither the scanning line driving circuits 110 nor thedata line driving circuit 112 needs to be provided directly on thesubstrate 102. The scanning line driving circuits 110 or the data linedriving circuit 112 may be provided on a substrate different from thesubstrate 102 (a semiconductor substrate or the like) or a connector anddrive the pixels 106. In the example of FIG. 1, the display region 108and the scanning line driving circuits 110 provided on the substrate 102are covered with the counter substrate 104, whereas the data signaldriving circuit 112 provided on a different substrate is mounted on thesubstrate 102.

The substrate 102 and the counter substrate 104 may each be a flexiblesubstrate. In this case, the substrate 102 may be called a “base film”or a “base plate”, and the counter substrate 102 may be called a “capfilm” or a “base plate”. In the case where the substrate 102 and thecounter substrate 104 are each a flexible substrate, the display device100 is flexible. The counter substrate 104 may be a resin film or acircularly polarizing plate.

FIG. 2 is a schematic exploded perspective view of the display device100. As shown in FIG. 2, the display device 100 includes an underlyingfilm 116 provided on, and in contact with, the substrate 102. Theunderlying film 116 does not need to cover the whole of a top surface ofthe substrate 102, and may partially cover the top surface of thesubstrate 102. Specifically, a part of the substrate 102 may be exposedfrom the underlying film 116 with no contact with the underlying film116. The underlying film 116 may contain an inorganic insulatingmaterial as described below. Therefore, the underlying film 116 may becalled an “inorganic insulating film”. In the display device 100, theplurality of pixels 106 are located in both of a region where theunderlying film 116 is provided and a region where the underlying film116 is not in contact with the substrate 102.

Various types of patterned insulating films and conductive films areprovided between the underlying film 116 and the counter substrate 104.A stack structure of these films forms the pixels 106, the scanning linedriving circuits 110, the data line driving circuit 112, and the like.

FIG. 3 is a schematic plan view of the display device 100. FIG. 3 showsthe substrate 102 and the underlying film 116 provided on the substrate102. In FIG. 3, the regions where the display region 108 and thescanning line driving circuits 110 are provided are represented bydashed lines. As described above, the underlying film 116 does not needto cover the whole of the substrate 102. Specifically, the underlyingfilm 116 is not provided on a partial region (first region) 120 of thesubstrate 102, and the top surface of the substrate 102 is exposed inthe first region 120 from the underlying film 116. In the example ofFIG. 3, the first region 102 of the substrate 102 is strip-like. Thesubstrate 102 also includes two regions (second regions) 122, which havethe first region 120 therebetween and are covered with the underlyingfilm 116. The underlying film 116 is divided by the first region 120 andis discontinuous between the two second regions 122. In other words, theunderlying film 116 has an opening or a slit, and the region of thesubstrate 102 in positional correspondence with the opening or the slitis the first region 120.

The first region 120 is provided to cross the display region 108, and apart of the plurality of pixels 106 (first pixels) overlap the firstregion 120. In this state, the pixels 106 overlapping the first region120 are arrayed in a matrix. By contrast, the two second regions 122overlap the display region 108 and a plurality of pixels 106 (secondpixels) included in the display region 108. Namely, the plurality ofpixels 106 overlapping each of the two second regions 122 are arrayed ina matrix. As shown in FIG. 3, the first region 120 may overlap thescanning line driving circuits 110.

FIG. 4 is a cross-sectional view of the display device 100 taken alongchain line A-A′ in FIG. 3. As shown in FIG. 4, the first region 120 ofthe substrate 102 is exposed from the underlying film 116. By contrast,the second regions 122 of the substrate 102 are in contact with theunderlying film 116. The first region 120 and the second regions 122both overlap the plurality of pixels 106. The plurality of pixels 106each include a display element such as a light emitting element 170 orthe like. Therefore, in the display device 100, the whole of the displayregion 108 overlapping the first region 120 and the second regions 122reproduces an image.

2. Cross-Sectional Structure

FIG. 5 is a schematic plan view of two adjacent pixels 106 eachincluding the light emitting element 170. In FIG. 5, the components areshown as not overlapping each other for visibility. A part of thecomponents may overlap each other. A part of the components is omittedin FIG. 5.

As shown in FIG. 5, the display device 100 includes wirings, such as aplurality of gate lines 132, a plurality of data lines 130, a pluralityof current supply lines 134 and the like. The gate lines 132 are eachelectrically connected with a plurality of pixels 106, and two of thepixels 106 are shown in FIG. 5. The data lines 130 and the currentsupply lines 134 are each connected with a plurality of pixels locatedalong the lines 130 and 134 respectively.

The pixels 106 each include transistors 140 and 150. The transistor 140includes a semiconductor film 142, a gate 144 (gate electrode), a drain146 (drain electrode), a source 148 (source electrode), and the like.The gate 144 is a part of the corresponding gate line 132, and drain 146is a part of the corresponding data line 130.

The transistor 150 includes a part of a semiconductor film 164, a gate152 (gate electrode), a drain 154 (drain electrode), a source 156(source electrode) and the like. The drain 154 is a part of thecorresponding current supply line 134. The source 148 of the transistor140 is connected with a first capacitor electrode 160 located in thesame layer as the gate line 132, and a part of the first capacitorelectrode 160 acts as the gate 152 of the transistor 150. Therefore, asignal generated by the data line driving circuit 112 and input from thedata line 130 is input to the gate 152 of the transistor 150 via thetransistor 140.

The semiconductor film 164 and a second capacitor electrode 162 areprovided to overlap the first capacitor electrode 160. Although notshown in FIG. 5, an insulating film acting as a gate insulating film 118of the transistor 140 and the transistor 150 is provided between thefirst capacitor electrode 160 and the semiconductor film 164 asdescribed below. An insulating film acting as an interlayer insulatinglayer (represented by reference numeral 124 in FIG. 6A and the like)covering the gate 144 of the transistor 140 and the gate 152 of thetransistor 150 is provided between the semiconductor film 164 and thesecond capacitor electrode 162. The first capacitor electrode 160, thegate insulating film 118, the semiconductor film 164, the interlayerinsulating film 124, and the second capacitor electrode 162 form acapacitor 158 (FIG. 6A and FIG. 6). The capacitor 158 contributes tomaintaining the potential of the gate 152 of the transistor 150.

The pixel 106 further includes a storage capacitor electrode 166. Thestorage capacitor electrode 166 may be electrically connected with thecorresponding current supply line 134. The pixel 106 includes a firstelectrode 172 acting as a pixel electrode. In FIG. 5, the firstelectrode 172 is not shown in the left pixel 106 for visibility. Thefirst electrode 172 is electrically connected with the source 156 of thetransistor 150. Although not shown in FIG. 5, the storage capacitorelectrode 166, the first electrode 172 and an insulating film providedbetween the storage capacitor electrode 166 and the first electrode 172form a storage capacitance. The storage capacitor contributes tomaintaining the potential of the gate 152 of the transistor 150.

Although not shown in FIG. 5, a second electrode 178 of the lightemitting element 170 is provided on the first electrode 172. The secondelectrode 178 is provided commonly for the plurality of pixels 106 andthus are shared by the plurality of pixels 106. An EL layer (not shownin FIG. 5; represented in FIG. 6A by reference numeral 188) is providedbetween the first electrode 172 and the second electrode 178. The lightemitting element 170 includes the first electrode 172, the secondelectrode 178 and the EL layer. Although not shown, the pixel 106 is notlimited to having the above-described structure. The pixel 106 mayfurther include another wiring, transistor, capacitor or the like.Alternatively, the pixel 106 does not need to include the storagecapacitor.

FIG. 6A and FIG. 6B are each a cross-sectional view of the displaydevice 100 taken along a chain line B-B′ in FIG. 5. FIG. 6A is aschematic cross-sectional view of the pixel 106 provided on the secondregion 122. FIG. 6B is a schematic cross-sectional view of the pixel 106provided on the first region 120.

As shown in FIG. 6A, the pixel 106 includes the underlying film 116provided on the second region 122 of the substrate 102. The underlyingfilm 116 may contain an inorganic insulating material. Examples of theinorganic insulating material usable for the underlying film 116 includesilicon-containing inorganic materials such as silicon oxide, siliconnitride, silicon nitride oxide, silicon oxide nitride, and the like. Theunderlying film 116 may have a single-layer structure or a stackstructure of a plurality of layers. In the example of FIG. 6A, theunderlying film 116 includes three layers (a first layer 116_1, a secondlayer 116_2 and a third layer 116_3). In this case, for example, thesecond layer 116_2 may contain silicon nitride, whereas the first layer116_1 and the third layer 116_3 may contain silicon oxide. The firstlayer 116_1, the second layer 116_2 and the third layer 116_3 mayrespectively have thicknesses of 20 nm to 50 nm, 20 nm to 50 nm, and 100nm to 500 nm.

On the second region 122, the transistor 150 is provided on theunderlying film 116. A part of the gate insulating film 118 of thetransistor 150, and the semiconductor film 164, may be in contact withthe underlying film 116.

A part of the semiconductor film 164 also acts as one electrode of thecapacitor 158. On the semiconductor film 164, the gate insulating film118 and the first capacitor electrode 160 are provided. The interlayerinsulating film 124 is provided to cover the first capacitor electrode160 and the gate 152. On the interlayer insulating film 124, the secondcapacitor electrode 162 overlapping the first capacitor electrode 160 isprovided. The second capacitor electrode 162 also acts as the source156.

Optionally, the pixel 106 may further include a first passivation film126 covering the transistor 150 and the capacitor 158.

On the transistor 150 and the capacitor 158, a flattening film 168 isprovided to absorb the ruggedness caused by these components and providea flat surface. The flattening film 168 has an opening, and the firstelectrode 172 of the light emitting element 170 is electricallyconnected with the source 156 of the transistor 150 via a connectionelectrode 180 in the opening.

On the flattening film 168, a partitioning wall 186 is provided toabsorb the ruggedness caused by the opening of the flattening layer 168and an end of the first electrode 172. The EL layer 188 and the secondelectrode 178 are provided on the first electrode 172 and thepartitioning wall 186. The light emitting element 170 includes the firstelectrode 172, the EL layer 188, and the second electrode 178.

Optionally, the pixel 106 may further include a second passivation film190 on the light emitting element 170. The second passivation film 190prevents entrance of impurities such as water, oxygen and the like fromoutside.

The counter substrate 104 is provided on the light emitting element 170or the second passivation film 190. Although not shown, an adhesivelayer or the like may be provided between the light emitting element 170or the second passivation film 190 and the counter substrate 104.

As shown in FIG. 6B, on the first region 120, the underlying film 116 isnot provided in the pixel 106. Therefore, for example, a part of thegate insulating film 118 may be in contact with the substrate 102. Thesemiconductor film 164 may also be in contact with the substrate 102.The structure of the pixel 106 on the first region 120 is the same asthat of the pixel 106 on the second region 122 except that theunderlying film 116 is not provided on the first region 120. Since theunderlying film 116 is not provided on the first region 120, theflattening layer 168 is thicker on the first region 120 than on thesecond region 122.

As described above, the underlying film 116 contains an inorganicinsulating material, and thus is more rigid than a film containing anorganic material. Therefore, when the display device 100 is bent orfolded to be deformed, the underlying film 116 is easily cracked.Generation of cracks causes wirings provided on the underlying film 116to be broken or disconnected. For example, the wirings such as the gateline 132, the data line 130, the current supply line 134 and the like,or the electrodes such as the first capacitor electrode 160, the secondcapacitor electrode 162, the storage capacitor electrode 166, the firstelectrode 172 and the like are broken or disconnected. As a result,light is not emitted from a part of or all of the pixels 106 in thedisplay device 100. In this case, the display device 100 does notfunction as a display device.

However, as shown in FIG. 3 and FIG. 4, the display device 100 includesthe first region 120, on which the underlying film 116 is provided. Thedisplay device 100 is bent in the first region 120 easily orselectively. In the case where, for example, the substrate 102, and thusthe display device 100, has a three-dimensional structure shown in FIG.7, the substrate 102 is bent in the first region 120 so that the displaydevice 100 is deformed such that the two second regions 122 overlap eachother. On the first region 120, the wiring or the electrodes are notbroken or disconnected due to the breakage of the underlying film 116.In this manner, the breakage or the disconnection of the wiring iseffectively suppressed. Thus, the breakage of the display device 100 isprevented. Therefore, the display device 100 in this embodiment ishighly reliable and flexible.

Embodiment 2

In this embodiment, a display device 200 having a different structurefrom that of the display device 100 will be described. Components thesame as or similar to those in embodiment 1 may not be described.

Unlike in the display device 100, in display device 200, the underlyingfilm 116 is provided both on the first region 120 and the second regions122, and the underlying film 116 is thinner on the first region 120 thanon the second regions 122.

FIG. 8A and FIG. 8B are each a cross-sectional view of the displaydevice 200 corresponding to cross section taken along a chain line B-B′in FIG. 5. FIG. 8A is a schematic cross-sectional view of the pixel 106provided on the second region 122. FIG. 8B is a schematiccross-sectional view of the pixel 106 provided on the first region 120.As shown in FIG. 8A, on the second region 122, the pixel 106 issubstantially the same as that in the display device 100. The underlyingfilm 116 is provided between the substrate 102 and the transistor 150,and the underlying film 116 is in contact with the substrate 102.

In the display device 200, a part of the underlying film 116 extendsfrom the second region 122 to the first region 120, and is sandwiched bythe transistor 150 in the pixel 106 and the first region 120 of thesubstrate 102. In the example of FIG. 86, the first layer 116_1 extendsfrom the second region 122 to the first region 120. Therefore, thenumber of the layer(s) of the underlying film 116 or the thickness ofthe underlying film 116 is smaller on the first region 120 than on thefirst region 120. Although not shown, the second layer 116_2 or thethird layer 1163 may extend to the first region 120 instead of the firstlayer 1161.

With such a structure, in embodiment 2, like in embodiment 1, the firstregion 120 is more flexible than the second regions 122, and the displaydevice 200 is deformed more easily in the first region 120 than in thesecond regions 122. Even though the first region 120 is bent to deformthe display device 200, the underlying film 116 is not easily cracked onthe first region 120 because the underlying film 116 is thinner on thefirst region 120. In this manner, the breakage or the disconnection ofthe wirings and the electrodes is suppressed. Thus, the breakage of thedisplay device 100 is prevented. Therefore, the display device 200 inthis embodiment is highly reliable and flexible.

Since the underlying film 116 is provided also on the first region 120,entrance of impurities such as alkaline ions or the like from the firstsubstrate 102 to the transistors 140 and 150 is prevented. This provideshigh reliability for the semiconductor element used to drive the displaydevice 200.

Embodiment 3

In this embodiment, a method for manufacturing the display device 100 inembodiment 1 will be described with reference to FIG. 6A, FIG. 6B andFIG. 9A through FIG. 17. Components the same as or similar to those inembodiment 1 may not be described. FIG. 9A through FIG. 17 eachcorrespond to FIG. 6A and FIG. 6B. FIG. 9A through FIG. 17 each providecross-sectional views of the pixels 106 on the second region 122 and thefirst region 120. The cross-sectional views in FIG. 9A through FIG. 17correspond to cross section taken along a chain line B-B′ in FIG. 5.

1. Underlying Film

As shown in FIG. 9A, the substrate 102 is formed on a support substrate128. The support substrate 128 has a function of supporting thesubstrate 102 and various other components formed on the substrate 102,for example, the transistors 140 and 150, the capacitor 158, the lightemitting element 170 and the like. Therefore, the support substrate 128may be formed of a material that is resistant against the temperature ofprocesses performed on the components to be formed thereon and ischemically stable against chemicals used in the steps. Specifically, thesupport substrate 128 may contain glass, quartz, plastics, a metal,ceramics or the like.

The substrate 102 is formed of a flexible insulating film, and maycontain, for example, a polymer material. Examples of the polymermaterial usable for the substrate 102 include a polyimide, a polyamide,a polyester, a polycarbonate and the like. These polymer materials maybe chain-like or may form a three-dimensional network by intermolecularcrosslinking. The substrate 102 may be formed by, for example, a wetfilm formation method such as printing, ink-jetting, spin-coating,dip-coating or the like, or by lamination. Alternatively, the substrate102 may be formed by forming precursors of any of the above-describedpolymer materials on the support substrate 128 and causing a polymerreaction of the precursors.

Next, as shown in FIG. 9A, the underlying film 116 is formed on thesecond region 122 of the substrate 102. As described above in embodiment1, the underlying film 116 may contain an inorganic insulating materialsuch as silicon nitride, silicon oxide, silicon nitride oxide, siliconoxide nitride or the like. The underlying film 116 may be formed bychemical vapor deposition (CVD), sputtering or the like to have asingle-layer structure or a stack structure. For example, the underlyingfilm 116 may be formed on substantially the whole of the top surface ofthe substrate 102, and then a part of the underlying film 116 that is onthe first region 120 may be selectively removed by etching. In the caseof having a stack structure, the underlying film 116 may include, forexample, a silicon nitride layer sandwiched between silicon oxidelayers. In the example of FIG. 9A, the underlying film 116 has athree-layer structure including the first layer 116_1, the second layer116-_2 and the third layer 116_3.

2. Transistors

Next, the semiconductor film 164 is formed in each of the pixels 106(FIG. 9B). The semiconductor film 164 may contain a Group 14 elementsuch as silicon or the like. Alternatively, the semiconductor film 164may contain an oxide semiconductor. Examples of the oxide semiconductorusable for the semiconductor film 164 include a Group 13 element such asindium, gallium or the like, for example, a mixed oxide of indium andgallium (IGO). In the case of containing an oxide semiconductor, thesemiconductor film 164 may further contain a Group 12 element. Examplesof the Group 12 element that may be contained in the semiconductor film164 include a mixed oxide containing indium, gallium and zinc (IGZO).There is no specific limitation to the crystallinity of thesemiconductor film 164. The semiconductor film 164 may be singlecrystalline, polycrystalline, microcrystalline or amorphous.Alternatively, these crystalline states may be mixed in thesemiconductor film 164.

In the case of containing silicon, the semiconductor film 164 may beformed by CVD using silane gas or the like as a raw material. Theobtained amorphous silicon may be heated or exposed to light such aslaser light or the like to be crystallized. In the case of containing anoxide semiconductor, the semiconductor film 164 may be formed bysputtering or the like.

Next, the semiconductor film 164 is subjected to first doping.Specifically, the first doping is performed as follows. A resist mask198 is formed on the semiconductor film 164 to cover a region where achannel of the transistor 150 is to be formed (FIG. 9B). In this state,the semiconductor film 164 is doped with ion. Examples of the usable ioninclude ion of phosphorus or nitrogen that provides n-type conductivityand ion of boron that provides p-type conductivity. After that, theresist mask 198 is removed. As a result, as shown in FIG. 10A, dopedregions 164_1 and an undoped region 164_2 are formed in thesemiconductor film 164.

Next, the gate insulating film 118 is formed to cover the semiconductorfilm 164 (FIG. 10A). The gate insulating film 118 may have asingle-layer structure or a stack structure. The gate insulating film118 may contain a material usable for the underlying film 116. The gateinsulating film 118 may be formed by CVD, sputtering or the like.

Next, the gate 152 and the first capacitor electrode 160 are formed onthe gate insulating film 118 by sputtering or CVD (FIG. 10B). The gate152 and the first capacitor electrode 160 are formed in the same layer.The gate 152 is formed to overlap the undoped region 164_2. The firstcapacitor electrode 160 is formed to overlap the doped region 164_1. Thegate 152 and the first capacitor electrode 160 may be formed of a metalsuch as titanium, aluminum, copper, molybdenum, tungsten, tantalum orthe like or an alloy thereof, and may be formed to have a single-layerstructure or a stack structure. For example, the gate 152 and the firstcapacitor electrode 160 may have a stack structure including a layer ofa highly conductive metal material such as aluminum, copper or the likeand a layer of a high melting point such as titanium, tungsten,molybdenum or the like formed on a layer of a metal with a highlyconductive metal. Alternatively, the gate 152 and the first capacitorelectrode 160 may have a structure in which a layer of a highlyconductive metal is sandwiched between layers of a metal with a highmelting point.

Next, the semiconductor film 164 is subjected to second doping with thegate 152 being used as a mask. The conditions for the second doping areadjusted such that the semiconductor film 164 is doped with a dopant ata lower concentration than in the first doping. As a result, lowconcentration impurity regions 164_3 are formed in a region of theundoped region 164_2 that does not overlapping the gate 152 (FIG. 11A).The low concentration impurity regions 164_3 have a lower concentrationof impurities than that of the doped regions 164_1. The undoped region164_2 is a region not doped with impurities or not substantially dopedwith impurities, and acts as a channel region.

Next, the interlayer insulating layer 124 is formed on the gate 152 andthe first capacitor electrode 160 (FIG. 11B). The interlayer insulatinglayer 124 may have a single-layer structure or a stack structure, andmay contain a material usable for the underlying film 116. Theinterlayer insulating layer 124 may be formed by CVD, sputtering or thelike.

Next, the interlayer insulating layer 124 and the gate insulating film118 are etched to form openings reaching the doped regions 1641 (FIG.11B). The openings may be formed, for example, by plasma etching in gascontaining a fluorine-containing hydrocarbon.

Next, a metal film is formed to cover the openings and is etched. As aresult, the source 156 and the drain 154 are formed (FIG. 12A). Thesource 156 also acts as the second capacitor electrode 162, andpartially overlaps the first capacitor electrode 160. A part of thedoped region 164_1 that overlaps the first capacitor electrode 160, apart of the gate insulating film 118 that overlaps the first capacitorelectrode 160, the first capacitor electrode 160, and a part of theinterlayer insulating film 124 that is sandwiched between the firstcapacitor electrode 160 and the second capacitor electrode 162, and thesecond capacitor electrode 162 form the capacitor 158. The capacitor 158contributes to maintaining the potential of the gate 152.

The metal film may contain a metal usable for the gate 152, and may havea single structure or a stack structure. The metal film may be formed bysputtering or CVD.

As a result of performing the above-described steps, the transistor 150is formed. The transistor 140 may be formed by substantially the sameprocess.

3. Intermediate Layers

Optionally, the first passivation film 126 may be formed on thetransistor 150 (FIG. 12A). The first passivation film 126 may have asingle-layer structure or a stack structure and may contain an inorganicinsulating material. Examples of the inorganic insulating materialusable for the first passivation film 126 include silicon-containinginorganic insulating materials such as silicon oxide, silicon nitride,silicon nitride oxide, silicon oxide nitride, and the like. The firstpassivation film 126 may be formed by sputtering or CVD.

Next, the flattening film 168 is formed (FIG. 12B). The flattening film168 absorbs the ruggedness caused by the transistor 150, the capacitor158 and the like and provides a flat surface. The flattening film 168may be formed of an organic insulating material. Examples of the organicinsulating material usable for the flattening film 168 include polymerssuch as an epoxy resin, an acrylic resin, a polyimide, a polyamide, apolyester, a polycarbonate, a polysiloxane, and the like. The flatteningfilm 168 may be formed by a wet film formation method described above.

Next, the flattening film 168 and the first passivation film 126 areetched to form an opening reaching the source 156 (FIG. 12B). Then, theconnection electrode 180 is formed to cover the opening (FIG. 13A). Theconnection electrode 180 may be formed of a light-transmissiveconductive oxide such as, for example, indium tin oxide (ITO), indiumzinc oxide (IZO) or the like, and may be formed by sputtering or thelike. It is not absolutely necessary to form the connection electrode180, but the connection electrode 180 protects exposed surfaces such asa surface of the source 156 and the like in subsequent steps and thusprevents increase in the contact resistance.

Although not shown, the storage capacitor electrode 166 (FIG. 5) may beformed after the formation of the connection electrode 180. The storagecapacitor electrode 166 may be formed of, for example, a metal such asaluminum, copper, titanium, molybdenum, tungsten, tantalum or the likeor an alloy thereof. The storage capacitor electrode 166 may have asingle-layer structure or a stack structure. For example, the storagecapacitor electrode 166 may have a structure ofmolybdenum/aluminum/molybdenum. The storage capacitor electrode 166forms a storage capacitor together with the first electrode 172 of thelight emitting element 170 to be formed in a later process.

Then, an insulating film 182 is formed (FIG. 13A). The insulating film182 also acts as a dielectric for the storage capacitance. Theinsulating film 182 may contain a material usable for the underlyingfilm 116 or the gate insulating film 118, exemplified by siliconnitride. The insulating film 182 may be formed by the same method asthat of the underlying film 116 or the gate insulating film 118. Theinsulating film 182 has an opening that exposes a part of a contactportion electrically connecting the transistor 150 and the lightemitting element 170 to each other (namely, that exposes a bottomsurface of the connection electrode 180 formed in the opening of theflattening film 168).

4. Light Emitting Element

Next, the first electrode 172 of the light emitting element 170 isformed (FIG. 13B). In the case where light from the light emittingelement 170 is output via the first electrode 172, the first electrode172 may be formed of a light-transmitting material, for example, aconductive oxide such as ITO, IZO or the like. By contrast, in the casewhere light from the light emitting element 170 is output from the sideopposite to the first electrode 172 (namely, via the second electrode178), the first electrode 172 may be formed of a metal such as aluminum,silver or the like or an alloy thereof. Alternatively, the firstelectrode 172 may have a stack structure of any of the above-listedmetal or an alloy thereof and a conductive oxide. For example, the firstelectrode 172 may have a stack structure in which a layer of a metal issandwiched between layers of a conductive oxide (e.g., ITO/silver/ITO,etc.).

After the first electrode 172 is formed, the partitioning wall 186 isformed (FIG. 14). The partitioning wall 186 has a function of absorbingthe steps caused by the end of the first electrode 172 and the openingformed in the flattening film 168, and also a function of electricallyinsulating the first electrodes 172 of the adjacent pixels 106 from eachother. The partitioning wall 186 is also referred to as a “bank” or a“rib”. The partitioning wall 186 may be formed of a material usable forthe flattening film 168. The partitioning wall 186 has an opening thatexposes a part of the first electrode 172, and an edge of the opening ispreferably moderately tapered. Such a shape prevents coverage failurefor the EL layer 188 or the second electrode 178 to be formed in a laterstep.

As shown in FIG. 13A, FIG. 13B and FIG. 14, an opening 184 may be formedin the insulating film 182 in order to allow the flattening film 168 andthe partitioning wall 186 to be in direct contact with each other. Sucha structure allows impurities such as water, desorbed from theflattening film 168, and the like to be released via the partitioningwall 186 in a heat treatment or the like performed after the formationof the partitioning wall 186.

After the formation of the partitioning wall 186, the EL layer 188 ofthe light emitting element 170 is formed, and the second electrode 178is formed on the EL layer 188 (FIG. 15). In the example of FIG. 15, theEL layer 188 has a three-layer structure including a first layer 174, asecond layer 175 and a third layer 176. The EL layer 188 is not limitedto having such a structure, and may have a single-layer structure or astack structure including four or more layers. For example, the EL layer188 may optionally include a charge injection layer, a charge transferlayer, a light emitting layer, a charge blocking layer, an excitonblocking layer or the like. Alternatively, one layer may have functionsof a plurality of layers. The EL layer 188 may be formed by vapordeposition, ink-jetting, printing, spin-coating or the like.

In the example of FIG. 15, the first layer 174 and the third layer 176of the EL layer 188 are respectively a charge injection layer and acharge transfer layer, or each have a stack structure of a chargeinjection layer and a charge transfer layer. The first layer 174 and thethird layer 176 may be formed commonly for the pixels 106 adjacent toeach other. Namely, the first layer 174 and the third layer 176 may beshared by the pixels 106. By contrast, the second layer 175 is a lightemitting layer, and although not shown, may be formed of a differentmaterial or may have a different structure among the pixels 106 adjacentto each other. Thus, the adjacent pixels 106 emit light of differentcolors. Alternatively, the second layer 175 may have a structure foremitting white light and may be formed to be shared by all the pixels106. In this case, color filters or the like may be used so that awavelength of light output from each pixel 106 is selected to providefull-color display.

After the formation of the EL layer 188, the second electrode 178 isformed (FIG. 15). The first electrode 172, the EL layer 188 and thesecond electrode 178 form the light emitting element 170. Carriers(electrons and holes) are injected from the first electrode 172 and thesecond electrode 178 into the EL layer 188, and the carriers arerecombined to provide an excited state. The excited state is relaxed toa ground state. As a result, light is emitted. Therefore, in the lightemitting element 170, a region where the EL layer 188 and the firstelectrode 172 are in direct contact with each other is a light emittingregion.

In the case where light from the light emitting element 170 is outputvia the first electrode 172, the second electrode 178 may be formed of ametal such as aluminum, silver or the like or an alloy thereof. Bycontrast, in the case where light from the light emitting element 170 isoutput via the second electrode 178, the second electrode 178 is formedof any of the above-listed metal or an alloy thereof and may be formedto have such a thickness so as to transmit visible light. Alternatively,the second electrode 178 may be formed of a light-transmitting material,for example, a conductive oxide such as ITO, IZO or the like. Stillalternatively, the second electrode 178 may have a stack structure ofany of the above-listed metal or an alloy thereof and a conductive oxide(e.g., Mg—Ag/ITO, etc.). The first electrode 172 and the secondelectrode 178 may be both formed by sputtering, CVD or the like.

As a result of performing the above-described steps, the light emittingelement 170 is formed.

5. Second Passivation Film

After the formation of the second electrode 178, the second passivationfilm 190 may be optionally formed. (FIG. 16). One of functions of thesecond passivation film 190 is to prevent entrance of moisture to thelight emitting element 170 from outside. It is preferable that thesecond passivation film 190 has a high level of gas barrier property.The second passivation film 190 may have any structure, and may have athree-layer structure (a first layer 192, a second layer 194, and athird layer 196) as shown in FIG. 16.

The first layer 192 may contain an inorganic material such as, forexample, silicon nitride, silicon oxide, silicon nitride oxide, siliconoxide nitride or the like, and may be formed by CVD, sputtering or thelike.

Next, the second layer 194 is formed. The second layer 194 may containan organic material such as an acrylic resin, a polysiloxane, apolyimide, a polyester or the like. As shown in FIG. 16, the secondlayer 194 may be formed to have a thickness so as to absorb theruggedness caused by the partitioning wall 186 and thus provide a flatsurface. The second layer 194 may be formed by a wet film formationmethod such as ink-jetting or the like. Alternatively, the second layer194 may be formed by gasiform or atomizing oligomers, which are amaterial of the above-described polymers, under a reduced pressure,spraying the oligomers to the first layer 192, and then polymerizing theoligomers.

Then, the third layer 196 is formed. The third layer 196 may contain amaterial usable for the first layer 192, and may be formed by the samemethod as that of the first layer 192.

6. Peeling Step

Then, as shown in FIG. 17, the counter substrate 104 is formed on thelight emitting element 170 or the second passivation film 190. Althoughnot shown, the counter substrate 104 may be bonded to the light emittingelement 170 or the second passivation film 190 with an adhesive layer.The counter substrate 104 may contain a polymer material like thesubstrate 102.

Then, light such as laser light or the like is applied to decrease theadhesive force between the support substrate 128 and the substrate 102.Next, a physical force is used to peel the support substrate 128 at theinterface between the support substrate 128 and the substrate 102(represented by the arrow in FIG. 17).

As a result of performing the above-described steps, the display device100 is produced.

Embodiment 4

In this embodiment, a display device 300 having a different structurefrom those in embodiment 1 and embodiment 2 will be described.Components the same as or similar to those in embodiments 1 and 2 maynot be described.

Similar to the display device 100 in embodiment 1, the substrate 102 ofthe display device 300 includes the first region 120 and the secondregions 122, and the underlying film 116 is provided on the secondregions 122. The second regions 122 overlap a plurality of pixels 106.The plurality of pixels 106 overlapping the second regions 122 arearrayed in a matrix. Unlike in the display device 100, in the displaydevice 300, the underlying film 116 is provided on a part of the firstregion 120. On the first region 120, a plurality of the underlying film116 are arrayed in stripes, and the underlying films 116 each have awidth smaller than the width or the length of each pixel 106. Therefore,in the display device 300, the underlying films 116 provided on thefirst region 120 overlap a plurality of pixels 106, but the plurality ofpixels 106 are not arrayed in a matrix.

FIG. 18 shows a specific structure of the display device 300. FIG. 18shows the substrate 102 and the underlying films 116 provided on thesubstrate 102. The regions where the display region 108 and the scanningline driving circuits 110 are provided are represented by dashed lines.As shown in FIG. 18, the substrate 102 includes the first region 120 andthe second regions 122 having the first region 120 therebetween. On apart of the first region 120, the underlying films 116 are provided. Forexample, as shown in the enlarged view in FIG. 18, the stripedunderlying films 116 are provided on the first region 120. On the firstregion 120, the striped underlying films 116 are located parallel to thecolumn direction of the pixels 106. On the first region 120, the pixels106 overlapping each underlying film 116 are not arrayed in a matrix butare arrayed in a straight line.

FIG. 19 shows an example of a cross-sectional structure of one pixel106. FIG. 19 is a schematic cross-sectional view corresponding to across-section taken along a chain line C-C′ in FIG. 5. FIG. 19 shows across-section of the pixel 106 on the first region 120. As shown in FIG.19, the underlying films 116 are selectively provided in a regionoverlapping the gate line 132 and the gate 144 of the transistor 140. Bycontrast, for example, in a region overlapping the second capacitor 162,no underlying film 116 is provided, and the semiconductor film 164 is incontact with the substrate 102. As shown in FIG. 19, the underlyingfilms 116 may be provided between the substrate 102 and a region of thesemiconductor film 142 or 164 that acts as a channel region of thetransistor 140 or 150.

Flexibility of substrate 102 is low in the region where the underlyingfilms 116 are provided. By contrast, the substrate 102 is highlyflexible and easily deformable in the region where no underlying film116 is provided. Therefore, when being deformed, the display device 300is preferentially deformed in the region where no underlying film 116 isprovided. Therefore, even though the display device 300 is bent in thefirst region 120, no significant load is applied to the underlying films116. Thus, the underlying films 116 are suppressed from being cracked.As a result, breakage and disconnection of the underlying films 116 andalso of the gate line 132 formed on the underlying films 116 areprevented. Therefore, the display device 300 in this embodiment ishighly reliable and flexible.

Embodiment 5

In this embodiment, display devices 400 and 410 having differentstructures from those in embodiments 1, 2 and 4 will be described.Components the same as or similar to those in embodiments 1, 2 and 4 maynot be described.

FIG. 20A is a plan view of the display device 400. FIG. 20A shows thesubstrate 102 and the underlying film 116 provided on the substrate 102.The regions where the display region 108 and the scanning line drivingcircuits 110 are provided are represented by dashed lines. As shown inFIG. 20A, the substrate 102 of the display device 400 includes aplurality of first regions 120 unlike the display devices 100, 200 and300. The number of the second regions 122 may be larger than the numberof the first regions 120. The first regions 120 are each sandwichedbetween the second regions 122. In the example of FIG. 20A, there aretwo first regions 120. Alternatively, three or more first regions 120may be provided. Since the plurality of first regions 120 are provided,the display device 400 may be bent or folded at a plurality ofpositions.

FIG. 20B is a schematic plan view of the display device 410. Similar toFIG. 20A, FIG. 20B shows the substrate 102 and the underlying film 116provided on the substrate 102. The regions where the display region 108and the scanning line driving circuits 110 are provided are representedby dashed lines. Unlike in the display device 100, 200 and 300, in thedisplay device 410, the first region 120 is provided in strips parallelto the longer side of the display region 108. In this case, the firstregion 120 may overlap the data line driving circuit 112 or theterminals 114. With such a structure, the display device 410 may be bentand deformed in a direction parallel to the shorter side so that ends ofthe display device 410 in the shorter side face each other.

Embodiment 6

In this embodiment, display devices 500, 510 and 520 having structuresdifferent from those in embodiments 1, 2, 4 and 5 will be described.Components the same as or similar to those in embodiments 1, 2, 4 and 5may not be described.

Unlike in the display devices 100, 200, 300, 400 and 410, in the displaydevice 500, a plurality of the display regions 108 are provided on thesubstrate 102, the plurality of display regions 108 are selectivelyprovided on the second regions 122, and the first region 120 is providedbetween the plurality of display regions 108.

FIG. 21 is a schematic plan view of the substrate 102 and the underlyingfilm 116 provided on the substrate 102 in the display device 500. InFIG. 21, the regions where the display region 108, the scanning linedriving circuits 110 and the like are provided are represented by dashedlines. As shown in FIG. 21, the substrate 102 of the display device 500includes the plurality of (two in FIG. 21) second regions 122, on whichthe underlying film 166 is provided. The substrate 102 further includesthe first region 120 between the two second regions 122. On the twosecond regions 122, display regions 108_1 and 1082 are providedrespectively. The display regions 108_1 and 108_2 each include aplurality of pixels 106. The pixels 106 do not overlap the first region120. The display regions 108_1 and 108_2 may be independently driven bythe scanning line driving circuits 110 or the like, and may reproducedifferent images from each other. The display regions 108_1 and 108_2may have similar shapes to each other, or may have different shapes orarea sizes from each other.

Wirings 136 extend from the terminals 144 to the pixels 106 via the dataline driving circuit 112. By contrast, wirings 138 extend from terminals115 to the scanning line driving circuits 110. The wirings 136 act as,for example, the data lines 130 or the current supply lines 134. Thewirings 136 are electrically connected with the pixels 106 in thedisplay region 108_1 closer to the terminals 114, and further cross thefirst region 120 and are electrically connected with the pixels 106 inthe display region 108_2 farther from the terminals 114. Similarly, thewirings 138 are electrically connected with the scanning line drivingcircuits 110 closer to the terminal 115, and further cross the firstregion 120 and are electrically connected with the scanning line drivingcircuits 110 farther from the terminal 115. Therefore, a connectermerely needs to be connected with one side of the display device 500 todrive both of two display regions 108_1 and 108_2.

The wirings 136 and 138 are not limited to being arranged in the layoutshown in FIG. 21. For example, as in a display device 510 shown in FIG.25, the wirings 136 may be located such that a part of or all of thewirings 136 extend from the terminals 114, cross the display region180_1 and a region overlapping the first region 120, extend between thedisplay region 180_2 and the scanning line driving circuits 110 fartherfrom the display region 180_1, and are connected with the display region180_2. In this case, in the display region 108_1, the pixels 106 aresequentially connected with the wirings 136 from the pixel closest tothe terminals 114. By contrast, in the display region 1082, the pixels106 are sequentially connected with the wirings 136 from the pixelfarthest from the terminals 114.

Alternatively, as shown in FIG. 26, the terminals 114 and 115connectable with the connector may be located along two sides of thesubstrate 102, so that neither the wirings 136 nor the wirings 138 arelocated on the first region 120. In a display device 520 having such alayout, the terminals 114 and 115 are located along two sides of thesubstrate 102 facing each other. The wirings 136 and 138 supplyingsignals to the display region 108_1 and the scanning line drivingcircuits 110 driving the display region 108_1 extend from the terminals114 and 115 located in the vicinity of the side of the display region108_1 that is opposite to the first region 120. By contrast, the wirings136 and 138 supplying signals to the display region 108_2 and thescanning line driving circuits 110 driving the display region 108_2extend from the terminals 114 and 115 located in the vicinity of theside of the display region 108_2 that is opposite to the first region120. With such a structure, the first region 120 is more easilydeformable.

FIG. 22 shows a cross-sectional structure of the display device 500.FIG. 22 is a cross-sectional view taken along a chain line D-D′ in FIG.21. As shown in FIG. 22, for example, the data line 130 extends from thedisplay region 108_1 to the display region 108_2. Although not shown,the current supply line 134 also extends from the display region 108_1to the display region 108_2 on the interlayer information film 124.

The first region 120 of the substrate 102 is in contact with the gateinsulating film 118. By contrast, the second regions 122 of thesubstrate 102 are in contact with the underlying film 116. Although notshown, on the first region 120, the underlying film 116 having a smallerthickness than on the second regions 122 may be provided, similar to inthe display device 200 in embodiment 2. In this case, on the firstregion 120, the gate insulating film 118 is in contact with theunderlying film 116 having such a smaller thickness.

The first region 120 with no underlying film 116 is more flexible thanthe second regions 122. Therefore, the first region 120 is more easilybendable than the second regions 122. The display device 500 may bestructured such that the wirings 136 and 138 are wider on the firstregion 120 than on the second region 122. For example, as shown in FIG.23A, the wirings 136 and the wirings 138 may be wider on the firstregion 120 than on the second region 122.

In this case, on the first region 120, the wirings 136 and the wirings138 (the wirings 136 in FIG. 23A) may have a symmetrical configurationwith respect to a straight line that is parallel to a direction in whichthe wirings 136 and 138 extend and passes the center of each of thewirings 136 and the wirings 138.

Alternatively, as shown in FIG. 23B, the wirings 136 and the wirings 138(only one wiring 138 is shown in FIG. 23B) may be shaped such that astraight line that is parallel to the direction in which the wirings 136and 138 extend and passes the center of the wider portion of each of thewirings 136 and the wirings 138 does not pass the thinner portionthereof. In this case, as shown in FIG. 23C, the wirings 136 and thewirings 138 (only one wiring 138 is shown in FIG. 23C) may each includestraight portions (in the circles in FIG. 23C) having a vectorperpendicular to the direction in which the wirings 136 and 138 extend,the straight portion being between the wider portion and the thinnerportion.

Still alternatively, as shown in FIG. 24, the wirings 136 and thewirings 138 may be structured to be partially wider as described aboveand also to include straight portions (in the circles in FIG. 24) havinga vector oblique to the direction in which the wirings 136 and 138extend. Such a structure improves the durability against bending orfolding, and prevents the wirings 136 and 138 from being broken ordisconnected.

In each of the display devices 500, 510 and 520, the underlying film 116is not provided on the first region 120, which is bent when the displaydevice 500, 510 or 520 is deformed. Alternatively, the underlying film116 is provided with a smaller thickness on the first region 120.Therefore, even though the display devices 500, 510 and 520 are eachdeformed in the first region 120, breakage or disconnection of thewirings or the electrodes is prevented from being caused by the cracksin the underlying line 116, and thus the breakage of the display deviceis prevented. Therefore, the display devices 500, 510 and 520 in thisembodiment are highly reliable and flexible.

The above-described embodiments and modifications according to thepresent invention may be appropriately combined as long as nocontradiction occurs. Devices described above in embodiments accordingto the present invention may have an element added thereto, or deletedtherefrom, or may be changed in design optionally by a person ofordinary skill in the art. Methods described above in embodimentsaccording to the present invention may have a step added thereto, ordeleted therefrom, or may be changed in a condition optionally by aperson of ordinary skill in the art. Such devices and methods areencompassed in the scope of the present invention as long as includingthe gist of the present invention.

In this specification, an EL display device is disclosed as an example.The embodiments of the present invention are also applicable to, forexample, a self-light emitting display device other than the EL displaydevice, a liquid crystal display device, an electronic paper-typedisplay device including an electrophoretic element or the like, or anyother flat panel display device. The embodiments of the presentinvention are applicable to small-, medium, large-size display deviceswith no specific limitation.

Even functions and effects that are different from those provided by theabove-described embodiments but are obvious from the description of thisspecification or are easily expectable by a person of ordinary skill inthe art are naturally construed as being provided by the presentinvention.

What is claimed is:
 1. A semiconductor device comprising: a base filmincluding a first region, a second region, and a third region, the firstregion being between the second region and the third region in a planarview; an inorganic insulating film on the base film, a part of theinorganic insulating film being in contact with the second region of thebase film, another part of the inorganic insulating film being incontact with the third region of the base film; a first transistorhaving a first semiconductor layer on the first region of the base film;and a second transistor having a second semiconductor layer on thesecond region of the base film, wherein the inorganic insulating film isabsent between the first semiconductor layer and the base film in thefirst region, the first semiconductor layer is in contact with the basefilm in the first region, and the part of the inorganic insulating filmis between the second region of the base film and the secondsemiconductor layer.
 2. The semiconductor device according to claim 1,further comprising a third transistor having a third semiconductor layeron the third trigon of the base film, wherein the another part of theinorganic insulating film is between the third region of the base filmand the third transistor.
 3. The semiconductor device according to claim1, wherein the base film is continuous in the first region, the secondregion, and the third region.
 4. The semiconductor device according toclaim 1, wherein the base film contains a polyimide.
 5. Thesemiconductor device according to claim 1, further comprising: a wiringextending between the second region and the second region through thefirst region continuously.
 6. The semiconductor device according toclaim 5, wherein the wiring has a first portion located on the firstregion and a second portion located on the second region, and a width ofthe first portion is greater than a width of the second portion.
 7. Thesemiconductor device according to claim 1, further comprising: aplanarization film covering the first region, the second region, and thethird region, wherein a thickness of the planarization film on the firstregion is greater than a thickness of the planarization film on thesecond region.
 8. The semiconductor device according to claim 1, furthercomprising; a gate insulating film covering the first semiconductorlayer and the second semiconductor layer, wherein in the first region,the gate insulating film is in contact with the base film, and in thesecond region, the gate insulating film is in contact with the inorganicinsulating film.